ORIGINAL ARTICLE: Detection of β-Lactamase Activity in Various Clinical Bacterial Isolates by Three Different Methods and its Correlation with Drug Resistance.

Background: β-lactams such as penicillins are the most widely used antibiotics, and β-lactamases are the greatest source of resistance to penicillins. Aims and Objectives: To study β-lactamase production in clinical isolates of family Enterobacteriaceae, P. aeruginosa and Staphylococci by three different methods and to correlate its potential with drug resistance; with an endeavour to evaluate convenient and economical method duly supported by relevant Minimum Inhibitory Concentration (MIC) studies. Material and Methods: Total 240 clinical isolates (Gram-negative bacilli-191, staphylococci-49) were subjected to antimicrobial susceptibility testing by Kirby-Bauer disk diffusion method and MIC for ampicillin and penicillin was determined by agar dilution method. β-lactamase was detected by broth acidometric, iodometric cell suspension and microbiological method. Results: Multidrug resistance was observed in more than 90% isolates. One hundred and ninety Gram-negative bacilli were resistant to ampicillin and 47 staphylococcal isolates were resistant to both penicillin and ampicillin. Though microbiological method gave highest positive results 210 (87.5%), iodometric method could detect β-lactamase in apparently sensitive isolates as well giving satisfactory [207 (86.25%)] comparable results. Conclusion: In view of the noted bacterial resistance, tests for β-lactamase should be carried out on a routine basis for an early implementation of appropriate antimicrobial therapy. Iodometric method is eminently convenient, economical and reliable method. Isolates showing MIC <0.125µg/ml for penicillin and MIC <8µg/ml for ampicillin should be checked for β-lactamase production

A STUDY OF VANCOMYCIN RESISTANT ENTEROCOCCI ISOLATED FROM URINARY TRACT INFECTIONS

Objective: Vancomycin resistant enterococci (VRE) are becoming a major emergence problem concern in urinary tract infection (UTI). This study provides accurate and complete description of antimicrobial susceptibility pattern and to know the prevalence of VRE in this area.Methods: A total of 3400 urine samples were collected and processed bacteriologically. The enterococci was isolated and identified by biochemical tests and Vitek 2. VRE was determined by disc diffusion, agar dilution and Vitek 2 automated machine. Statistical analysis was done by Graph Pad InStat Software.Results: The 143 (4.2%) enterococci were isolated from UTI patients. The incidence was higher in young females and old males. E. faecalis (78%) is the most common isolate followed by E. faecium (15%). The rare species (9%) like E. durans, E. avium, E. gallinarum and E. hirae were also isolated. Fosfomycin (96.5%) and nitrofurantoin (93%) was the drug of choice for enterococcal UTI while linezolid (98.6%) also can be used to treat other enterococcal infections. Among the UTI 98.6% enterococci were susceptible to vancomycin.Conclusion: Empirical therapy for enterococcal infections should be guided by local patterns of drug resistance. Linezolid, fosfomycin or nitrofurantoin may be considered to treat the patients with VRE.Â

DETECTION OF METALLO BETA - LACTAMASES AMONG ENTEROBACTERIACEAE ISOLATES AT A TERTIARY CARE HOSPITAL, SOUTH INDIA

Background: The spread of carbapenem resistant bacteria has caused grave concern due to the limited choice in antibiotics for treating infections caused by them. The emergence of  metallo beta-lactamse (MBL) producing  gram negative bacilli poses a therapeutic challenge and is of serious concern for infection control in hospital environment. Materials &amp; Methods: A total of 475 non repeat clinical isolates of family Enterobacteriaceae were included in the study. Resistance to imipenem was determined in isolates by disc diffusion &amp; minimum inhibitory concentration (MIC) method. Imipenem resistant  isolates  were tested for MBL production by combined disc diffusion test and modified Hodge test. Results: Out of the 475 Enterobacteriaceae strains,  20 showed resistance to imipenem. MBL activity was detected in all 20 (4.2%) isolates by combined disc diffusion test, in 18 isolates by modified Hodge test. The MBL producing isolates included clinical strains of Klebsiella spp (45%), E. coli (40%), Citrobacter spp (15%).  Majority of the MBL isolates were from Intensive care unit (65%), from patients with comorbid conditions and with invasive devices.  MBL producing isolates showed high level of resistance to aminoglycosides and fluoroquinolones but all were susceptible to colistin. Conclusion: The need of the hour is to detect MBL producing isolates for better patient outcomes, to execute prompt infection control measures and decrease the escalation of resistance